They can't be other sides of the same stone if you check their position relative to the rest of the installation.
I wish the need for confirmation were a matter of inspiration levels for me, I'd use my free time much more judiciously. Since I have to know before hit "Submit," here we go. Funny how the detonator goes off at 4:03:33 am. The parking area and streetlight are off to the left of the frame and the explosion happens on the right.
Per Jimmy Wales: "The names of eight modern languages are inscribed along the long edges of the projecting rectangles, one per edge. Starting from due north and moving clockwise around so that the upper edge of the northeast rectangle is listed first, they are English, Spanish, Swahili, Hindi, Hebrew, Arabic, Chinese, and Russian."
The parking lot is to the north and the camerapole is to the Southwest, so I'm concluding the stone that got detonated was the "Swahili, Hindi" slab.
Note that setting up a charge behind it would allow you to park and exit a vehicle without showing up on that camera, too.